A sheet of wrapping material wrapped about a group of cigarettes comprises a flat wall defined by a portion of the sheet of wrapping material contacting the group.
One known method of transferring wrappings of the above type comprises feeding the wrappings along a path by means of a pocket conveyor, each pocket of which houses a wrapping having a flat wall substantially free of the pocket; and guiding the wrappings by means of a guide facing the pockets and contacting the wrappings along said path.
When the pockets travel along a straight path, the guide is defined by a fixed plate having a flat sliding face, along which the wrapping slides in use. Automatic machine manufacturers, however, prefer to transfer packets of cigarettes on wheel conveyors, which are more reliable than chain or belt conveyors, so that the path of the pockets and relative fixed guide is curved as opposed to straight. Though performing the same functions as a straight guide, such as retaining the wrappings inside the pockets, a curved guide has disadvantages caused by the flat wall of the wrapping sliding along a curved sliding surface of the guide, so that the wrapping contacts the guide at edges on opposite sides of the flat wall. Just some of the disadvantages of the wrapping contacting the guide in this way are wear of the wrapping along the edges, deformation of the edges, and deformation of the flat wall, which tends to reproduce the curve of the guide under the centrifugal force of the group of cigarettes.
Deformation of the flat wall is further compounded when the wrapping, as it travels along the curved path, is subjected to folding, e.g. finish folding, operations which may induce deformation along the flat wall. In particular, folding portions of the wrapping directly connected to the flat wall induce deformation of the flat wall, unless the whole of the flat wall is supported.